[Patent document 1] JP-2003-206781 A
[Patent document 2] JP-2001-207883 A
[Patent document 3] JP-2007-56734 A
[Patent document 4] JP-2006-316644 A
In recent years, there is seen an idling stop, which stops an engine at a time when a vehicle stops, for a purpose of saving an energy and reducing an environmental load. In order to perform an idling stop effectively, it is necessary to appropriately designate a time for stopping an engine and a time for starting the engine. Such an engine stop time and an engine start time for a subject vehicle are determined conventionally based on so-called vehicle-to-vehicle communications, a distance up to an intersection, a display status of a traffic light, or a state of a preceding vehicle just ahead of the subject vehicle (refer to Patent documents 1 to 4).
Naturally, the determining of the engine start time based on the vehicle-to-vehicle communications requires each vehicle to have a vehicle-to-vehicle communications apparatus. The penetration rate of the vehicle-to-vehicle communications apparatuses is still low under the present circumstances; thus, the idling stop using the vehicle-to-vehicle communications has little practicality presently, posing a problem. In addition, if the determination of the engine start time is made only based on the distance up to the intersection or the display status of the traffic light, the engine start time may be determined regardless of the actual road traffic states. Thus, for example, even though the subject vehicle cannot start forward movement, there is a possibility that the engine may be started. Such a case causes a useless fuel to be consumed to reduce a fuel efficiency, posing a problem. In addition, if the determination of the engine start time is made based on the state of a preceding vehicle ahead of the subject vehicle, a time delay arises from when the preceding vehicle starts forward movement to when the subject vehicle starts forward movement. This poses a problem to worsen a manipulability.